In recent years, a technology called a M2M (Machine to Machine) service has been developed in which environmental data such as temperature, illuminance, and humidity are measured by a node apparatus equipped with a sensor and others and the measured data are collectively collected via wireless communications. For example, in a M2M service in the field of agriculture, pieces of information about temperature, water content in soil, and others detected by a node apparatus equipped with a sensor installed in a farm are collected with a wireless communication function of the node apparatus to one place, thereby managing the growth of crop.
A system to which this M2M service is applied includes a data collecting apparatus as a gateway for wireless communication with a plurality of node apparatuses associated with respective data collecting apparatuses. With these data collecting apparatuses communicating with their corresponding node apparatuses, data in the node apparatuses are collected.
However, in the system to which the M2M service is applied, there is a problem of interference arising between data collecting apparatuses. That is, radio waves from the data collecting apparatuses interfere with each other when the data collecting apparatuses are adjacently arranged and communicate in parallel with the node apparatuses by using a communication channel of the same frequency. As a technology for avoiding this interference between data collecting apparatuses, there is a technology in which a data collecting apparatus transmits and receives a beacon signal to and from another data collecting apparatus by using a common channel. In this technology, when one data collecting apparatus receives a beacon signal containing information indicating a data collection time of another data collecting apparatus, the data collecting apparatus specifies a time other than the data collection time of the other data collecting apparatus as a non-interference time, and acquires its own data collection time from the non-interference time.
Japanese Laid-open Patent Publication No. 2006-254398 is an example of related art.